The Principles of Biology, Volume 2 (of 2)

Part Iv., With Which This Volume Commences, Contains Numerous Figures.

Nearly one half of them are repetitions, mostly altered in scale and simplified in execution, of figures, or parts of figures, contained in the works of various Botanists and Zoologists. Among the authors whom I have laid under contribution, I may name Berkeley, Carpenter, Cuvier, Green, Harvey, Hooker, Huxley, Milne-Edwards, Ralfs, Smith. The remaining figures, numbering 150, are from original sketches and diagrams.

The successive instalments which compose this volume, were issued to the Subscribers at the following dates:--No. 13 (pp. 1–80) in January, 1865; No. 14 (pp. 81–160) in June, 1865; No. 15 (pp. 161–240) in December, 1865; No. 16 (pp. 241–320) in June, 1866; No. 17 (pp. 321–400) in November, 1866; and No. 18 (pp. 401–566) in March, 1867.

LONDON, March 23rd, 1867.

CONTENTS OF VOL. II.

Part Iv.--Morphological Development.

CHAP. PAGE

I.--THE PROBLEMS OF MORPHOLOGY 3

II.--THE MORPHOLOGICAL COMPOSITION OF PLANTS 17

III.--THE MORPHOLOGICAL COMPOSITION OF PLANTS--Continued 37

IV.--THE MORPHOLOGICAL COMPOSITION OF ANIMALS 85

V.--THE MORPHOLOGICAL COMPOSITION OF ANIMALS--Continued 111

VI.--MORPHOLOGICAL DIFFERENTIATION IN PLANTS 128

VII.--THE GENERAL SHAPES OF PLANTS 134

VIII.--THE SHAPES OF BRANCHES 145

IX.--THE SHAPES OF LEAVES 152

X.--THE SHAPES OF FLOWERS 161

XI.--THE SHAPES OF VEGETAL CELLS 175

XII.--CHANGES OF SHAPE OTHERWISE CAUSED 178

XIII.--MORPHOLOGICAL DIFFERENTIATION IN ANIMALS 183

XIV.--THE GENERAL SHAPES OF ANIMALS 186

XV.--THE SHAPES OF VERTEBRATE SKELETONS 209

XVI.--THE SHAPES OF ANIMAL CELLS 228

XVII.--SUMMARY OF MORPHOLOGICAL DEVELOPMENT 231

Part V.--Physiological Development.

I.--THE PROBLEMS OF PHYSIOLOGY 239

II.--DIFFERENTIATIONS BETWEEN THE OUTER AND INNER TISSUES OF PLANTS 244

III.--DIFFERENTIATIONS AMONG THE OUTER TISSUES OF PLANTS 251

IV.--DIFFERENTIATIONS AMONG THE INNER TISSUES OF PLANTS 272

V.--PHYSIOLOGICAL INTEGRATION IN PLANTS 292

VI.--DIFFERENTIATIONS BETWEEN THE OUTER AND INNER TISSUES OF ANIMALS 299

VII.--DIFFERENTIATIONS AMONG THE OUTER TISSUES OF ANIMALS 309

VIII.--DIFFERENTIATIONS AMONG THE INNER TISSUES OF ANIMALS 323

IX.--PHYSIOLOGICAL INTEGRATION IN ANIMALS 373

X.--SUMMARY OF PHYSIOLOGICAL DEVELOPMENT 384

X^A.--THE INTEGRATION OF THE ORGANIC WORLD 396

Part Vi.--Laws of Multiplication.

I.--THE FACTORS 411

II.--À PRIORI PRINCIPLE 417

III.--OBVERSE À PRIORI PRINCIPLE 424

IV.--DIFFICULTIES OF INDUCTIVE VERIFICATION 432

V.--ANTAGONISM BETWEEN GROWTH AND ASEXUAL GENESIS 439

VI.--ANTAGONISM BETWEEN GROWTH AND SEXUAL GENESIS 448

VII.--THE ANTAGONISM BETWEEN DEVELOPMENT AND GENESIS, ASEXUAL AND SEXUAL 461

VIII.--ANTAGONISM BETWEEN EXPENDITURE AND GENESIS 467

IX.--COINCIDENCE BETWEEN HIGH NUTRITION AND GENESIS 475

X.--SPECIALITIES OF THESE RELATIONS 486

XI.--INTERPRETATION AND QUALIFICATION 497

XII.--MULTIPLICATION OF THE HUMAN RACE 506

XIII.--HUMAN POPULATION IN THE FUTURE 522

APPENDICES.

A.--SUBSTITUTION OF AXIAL FOR FOLIAR ORGANS IN PLANTS 541

B.--A CRITICISM ON PROF. OWEN’S THEORY OF THE VERTEBRATE SKELETON 548

C.--ON CIRCULATION AND THE FORMATION OF WOOD IN PLANTS 567

D.--ON THE ORIGIN OF THE VERTEBRATE TYPE 599

D^2.--THE ANNULOSE TYPE 602

E.--THE SHAPES AND ARRANGEMENTS OF FLOWERS 608

F.--PHYSIOLOGICAL (OR CONSTITUTIONAL) UNITS 612

G.--THE INHERITANCE OF FUNCTIONALLY-CAUSED MODIFICATIONS 618

PART IV.. Morphological Development.

MORPHOLOGICAL DEVELOPMENT.

CHAPTER I.

THE PROBLEMS OF MORPHOLOGY.

§ 175. The division of Morphology from Physiology, is one which may be tolerably-well preserved so long as we do not carry our inquiries beyond the empirical generalizations of their respective phenomena; but it is one which becomes in great measure nominal, when the phenomena are to be rationally interpreted. It would be possible, after analyzing our Solar System, to set down certain general truths respecting the sizes and distances of its primary and secondary members, omitting all mention of their motions; and it would be possible to set down certain other general truths respecting their motions, without specifying their dimensions or positions, further than as greater or less, nearer or more remote. But on seeking to account for these general truths, arrived at by induction, we find ourselves obliged to consider simultaneously the relative sizes and places of the masses, and the relative amounts and directions of their motions. Similarly with organisms. Though we may frame sundry comprehensive propositions respecting the arrangements of their organs, considered as so many inert parts; and though we may establish several wide conclusions respecting the separate and combined actions of their organs, without knowing anything definite respecting the forms and positions of these organs; yet we cannot reach such a rationale of the facts as the hypothesis of Evolution aims at, without contemplating structures and functions in their mutual relations. Everywhere structures in great measure determine functions; and everywhere functions are incessantly modifying structures. In Nature the two are inseparable co-operators; and Science can give no true interpretation of Nature without keeping their co-operation constantly in view. An account of organic evolution, in its more special aspects, must be essentially an account of the interactions of structures and functions, as perpetually altered by changes of conditions.

Hence, when treating apart Morphological Development and Physiological Development, all we can do is to direct our attention mainly to the one or to the other, as the case may be. In dealing with the facts of structure, we must consider the facts of function only in such general way as is needful to explain the facts of structure; and conversely when dealing with the facts of function.

§ 176. The problems of Morphology fall into two distinct classes, answering respectively to the two leading aspects of Evolution. In things which evolve there go on two processes--increase of mass and increase of structure. Increase of mass is primary, and in simple evolution takes place almost alone. Increase of structure is secondary, accompanying or following increase of mass with more or less regularity, wherever evolution rises above that form which small inorganic bodies, such as crystals, present to us. As the fundamental antagonism between Dissolution and Evolution consists in this, that while the one is an integration of motion and disintegration of matter, the other is an integration of matter and disintegration of motion; and as this integration of matter accompanying disintegration of motion, is a necessary antecedent to the differentiation of the matter so integrated; it follows that questions concerning the mode in which the parts are united into a whole, must be dealt with before questions concerning the mode in which these parts become modified.

This is not obviously a morphological question. But an illustration or two will make it manifest that fundamental differences may be produced between aggregates by differences in the degrees of composition of the increments: the ultimate units of the increments being the same. Thus an accumulation of things of a given kind may be made by adding one at a time. Or the things may be tied up into bundles of ten, and the tens placed together. Or the tens may be united into hundreds, and a pile of hundreds formed. Such unlikenesses in the structures of masses are habitually seen in our mercantile transactions. Articles which the consumer recognizes as single, the retailer keeps wrapped up in dozens, the wholesaler sends in gross, and the manufacturer supplies in packages of a hundred gross. That is, they severally increase their stocks by units of simple, of compound, and of doubly-compound kinds. Similarly result those differences of morphological composition which we have first to consider. An organism consists of units. These units may be aggregated into a mass by the addition of unit to unit. Or they may be united into groups, and the groups joined together. Or these groups of groups may be so combined as to form a doubly-compound aggregate. Hence there arises respecting each organic form the question--is its composition of the first, second, third, or fourth order?--does it exhibit units of a singly-compounded kind only, or are these consolidated into units of a doubly-compounded kind, or a triply-compounded kind? And if it displays double or triple composition, the homologies of its different parts become problems. Under the disguises induced by the consolidation of primary, secondary, and tertiary units, it has to be ascertained which answer to which, in their degrees of composition.

Such questions are more intricate than they at first appear; since, besides the obscurities caused by progressive integration, and those due to accompanying modifications of form, further obscurities result from the variable growths of units of the different orders. Just as an army may be augmented by recruiting each company, without increasing the number of companies; or may be augmented by making up the full complement of companies in each regiment, while the number of regiments remains the same; or may be augmented by putting more regiments into each division, other things being unchanged; or may be augmented by adding to the number of its divisions without altering the components of each division; or may be augmented by two or three of these processes at once; so, in organisms, increase of mass may result from additions of units of the first order, or those of the second order, or those of still higher orders; or it may be due to simultaneous additions to units of several orders. And this last mode of integration being the general mode, puts difficulties in the way of analysis. Just as the structure of an army would be made less easy to understand if companies often outgrew regiments, or regiments became larger than brigades; so these questions of morphological composition are complicated by the indeterminate sizes of the units of each kind: relatively-simple units frequently becoming more bulky than relatively-compound units.

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